1. Field of the Invention
This invention concerns an activating device having an electric circuit to switch ON and OFF any kind of electric device, such as a motor driven device. More specifically, it concerns an activating device having an electric circuit to switch any type of switching system in which at least one switching unit among a plurality of switching units must be switched ON or OFF safely without failure. For example, the activating device of this invention could be used to switch a motor ON and OFF to open and close power windows in an automobile, even when that automobile is submerged in water.
2. Background of the Invention
Most motor drive systems for opening and closing power windows in automobiles have an electronic control system capable of an automatic reverse function for the power windows and a multiplex communication control function. The motor serves as the drive source for the power windows. The most common way to supply appropriate power to the motor and to control its operation is to use a drive method using relays. Typical configurations of motor drive devices of the prior art are shown in FIGS. 3 and 4.
In the conventional motor drive device according to the prior art, the motor activating device for an automobile power window has two relays, a first relay 2 and a second relay 3, for supplying power to the motor 1. The first relay 2 drives the motor in reverse (as when closing the window of an automobile), while the second relay 3 drives the motor in a forward direction (as when opening the window of an automobile). Two operating switches, a first operating switch 4 and a second operating switch 5, activate the motor 1 to operate the power window in the close and open directions.
The first and second relays 2 and 3 include coils 2a and 3a, respectively, which create magnetic force, and first and second contacts 2b and 3b, respectively. The first and second contacts 2b and 3b each have a common terminal C, a normal open terminal (N.O. terminal) and a normal close terminal (N.C. terminal). When the electric current is not flowing through the first and second coils 2a and 3a so that the relays are not in operation, the C terminals and the N.C. terminals are in contact with each other. When electric current is flowing through the first and second coils 2a and 3a, the C terminals and the N.O. terminals are in contact with each other.
The N.O. terminals of the first and second relays 2 and 3 are connected to a power supply E, typically the automobile battery, while the N.C. terminals are connected to ground. The C terminal of first relay 2 is connected to the reverse terminal of the motor where the motor closes the window if the terminal is connected to the power supply side. The C terminal of second relay 3 is connected to the forward terminal of the motor. The motor opens the window if the forward terminal is connected to the power supply side.
The first and second operating switches 4 and 5, respectively, each have a contact which is actuated when the driver operates the switches. A rotating switch unit is typically used for these two operating switches 4 and 5. The operating switch 4 will go ON if the rotating switch rotates in one direction for closing the automobile window, while switch 5 will go ON if it rotates in the other direction for opening the automobile window.
In the configuration shown in FIG. 3, the first and second coils 2a and 3a of first and second relays 2 and 3 can be connected to a line from the power supply by means of the operating switches 4 and 5. Making and breaking the respective switching contact of the operating switches directly opens and closes this line from the power supply. In another configuration as shown in FIG. 4, the operating switches 4 and 5 are provided in the ground line of the first and second coils 2a and 3a of the first and second relays 2 and 3. This configuration is also of the type in which the switching contact directly opens or closes the connection between each relay coil and the ground line.
In both the configurations shown in FIGS. 3 and 4, there are two ON-OFF transistors, (11 and 12 in FIG. 3, and 11a and 12a in FIG. 4), and a signal processor (13 in FIG. 3 and 13a in FIG. 4), which causes the motor to run in a given direction based on a remote signal from a remote window opener or on a particular situation at a given moment, and which outputs a drive signal to actuate one of the aforesaid transistors. These transistors and the signal processor are on either the ground or power supply side of the first and second coils 2a and 3a of the first and second relays 2 and 3. Signal processor 13 (or 13a) is typically a single-chip microprocessor. In the circuit in FIG. 3, it drives transistors 11 and 12 through transistors 14 and 15.
In this configuration, the input lines (16 and 17 in FIG. 3 and 16a and 17a in FIG. 4) connect one terminal of the first and second operating switches 4 and 5 to the input terminal of the signal processor 13, which monitors the open/closed state (i.e., the ON/OFF state) of the operating switches 4 and 5.
In both FIGS. 3 and 4, an automatic mode switch 18 inputs an "automatic window close" command to signal processor 13 in response to the actuation of an automatic operating unit.
In the drive circuits described above, the drive operation of the motor 1 is directly controlled by opening or closing one of the terminals for the coils 2a and 3a in the relays 2 and 3, respectively. This control is performed by the operating switch 4 or S.
When the first operating switch 4 is actuated and its contact closes, the voltage from the power supply E causes current to flow into the first coil 2a, which magnetizes the first relay 2, thereby causing only the first contact 2b to operate. When the first operation switch 4 is activated, only the reverse terminal la of the motor is connected, through the C and N.O terminals of first contact 2b, to the power supply E, so the motor runs in reverse, causing the automobile window to close.
When the switch 5 is actuated and its contact closes, the voltage from the power supply E causes current to flow into the second coil 3a, which magnetizes the second relay 3, thereby causing only the second contact 3b to operate. In this case, only the forward terminal 1b of the motor is connected, through the C and N.O terminals of the second contact 3b, to the power supply E, so the motor runs forward, causing the automobile window to open.
With the drive circuits described above, the signal processing function of the signal processor 13 (or 13a) allows the operation of the motor 1 in a specified direction to be controlled in response to a radio signal input from the exterior even though neither the operating switch 4 nor switch 5 has been actuated, i.e., the motor is remotely controlled.
The signal processor 13 (or 13a) reads the current value and rpm of the motor 1 while it is running in reverse (i.e., while the window is closing). If the signal processor determines from the current value and other data that the window is jammed, the signal processing function of the signal processor 13 (or 13a) forces the motor 1 to run forward and open the window even though the switch 5 has not been actuated (auto-reverse function).
If the automatic switch 18 is actuated, the signal processing function of the signal processor 13 (or 13a) will cause the motor 1 to automatically reverse until it is pre-determined, via a detection signal from a limit switch (not shown), that the window is completely closed (automatic close function).
When the signal processor 13 (or 13a) must the drive motor 1 in the forward direction in order to execute the aforesaid remote control or auto-reverse function, it outputs a drive signal only to the transistor 12 (or 12a) to switch the transistor ON. When the transistor 12 (or 12a) goes ON, as can be seen in FIGS. 3 and 4, current flows into the second coil 3a of the second relay 3 without the operation of the second operating switch 5. The second contact 3b is actuated and the motor 1 operates in the forward direction to open the window.
When the signal processor 13 (or 13a) must drive the motor 1 in reverse in order to execute the aforesaid communication control or automatic close function or the like, it outputs a drive signal only to the transistor 11 (or 11a) to switch the transistor ON. When the transistor 11 (or 11a) goes ON, as can be seen in FIGS. 3 and 4, current flows into the first coil 2a of the first relay 2 regardless of the operating state of the first operating switch 4. The first contact 2b is actuated and the motor 1 operates in reverse to close the window.
With the activating device for a motor which is described above, if the automobile plunges into the ocean or a lake and the activating device is immersed, the water may cause current to flow (in other words, leak) to the contacts of the first and second operating switches 4 and 5 even though the driver did not actuate the switches. In that case, even if the second operating switches 4 and 5 are actuated, the motor 1 will not run in either direction.
In other words, if the water has a sufficient electrolyte concentration, both the first and second operating switches 4 and 5 will close so that the leakage current will flow into both of the first and second coils 2a and 3a. If this leakage current is sufficiently large, the first and second contacts 2b and 3b of the first and second relays 2 and 3 will be both actuated. As a result, both of the terminals 1a and 1b of the motor 1 will be connected to the power supply. If thereafter the first and second operating switches 4 and 5 are actuated manually, or the signal processor 13 (or 13a) outputs a drive signal to one of the transistors, the motor 1 will remain inoperable because the motor 1 will no longer have a ground connection, and the state of the circuit constituting the channel which leads to the motor 1 will remain unchanged.
It is conceivable that the aforesaid problem could be addressed by making sure that the first and second operating switches 4 and 5 have a watertight design. However, in practical terms this is far from easy to accomplish. Operating switches 4 and 5 must have contacts which are operated mechanically by a pushbutton unit which must remain exposed in the driver's compartment. This makes it difficult to mold the contacts, because the configuration required to provide a watertight seal is extremely complicated.
The present applicants previously solved the problem which occurs as described above when an automobile is submerged by providing an actuating device for a motor with an interlock switch system. When one of the relays is actuated, both terminals of the coil in the other relay are shorted to insure that it is not possible to actuate that relay.
However, interlocking the operation of an ordinary switch so that the terminals of the coil in the other relay are shorted requires a new switch contact. This makes the configuration which contains the operating unit and the switch contacts more complex, with the result that the device must be somewhat bulkier and more expensive.